1. Field of the Invention
The present invention relates to a differential speed reducer for extremely high speed reduction. More particularly, it relates to such a device having an input shaft and an output shaft driven by one or more orbital bevel pinions.
2. The Prior Art
Various types of speed reducers are known. One example is disclosed in F'Geppert, U.S. Pat. No. 4,310,146. The patent discloses a speed reducer mechanism which couples a motor shaft to a winding drum for use as a winch. The speed reducer includes two bevel gears driven by the motor shaft at slightly different speeds in opposite directions. A third bevel pinion gear simultaneously meshes with the oppositely rotating bevel gears so that the third gear is caused to slowly orbit around the motor shaft axis. The winding drum is carried by the third gear and thus rotates at the third gear speed. Speed reduction in the area of up to 400:1 is obtainable by use of the apparatus.
Although the patent may be useful in providing a high torque winding drum, it is not suited for other applications where the output is desirably transmitted along a shaft. In other words, an output shaft cannot be provided according to the patent due to the internal configuration of the gears.
Epicyclic gear trains are also known for use as speed reducers. In such a device, a pinion gear mounted on an arm orbits between a spur gear and a ring gear. The difference in speeds of the spur gear and ring gear cause the pinion gear to orbit, driving an output shaft connected to the arm.